For example, a heat exchanger recited in Patent Literature 1 includes a tank that is formed by using synthetic resin, in which glass fibers are added as a reinforcing material.
As shown in FIGS. 16 and 17, this tank 100 has a cross-section, in which a ceiling portion is curved, and this tank 100 forms an opening that is configured into a generally rectangular form (a generally oblong form). Furthermore, the tank 100 has a tank foot 110, which extends all around the opening of the tank 100. A core plate is fixed to the tank foot 110 by crimping through an undepicted packing. At the time of molding the tank 100, in view of good flow of the resin and shortening of the filling time of the resin, an opening of a gate G at a cavity of an injection molding die, i.e., a gate position GP (indicated with an arrow in the drawing), which forms a filling port of the resin, is often placed in a longitudinal end part of the tank 100 (a lateral surface of the tank 100), as shown in FIG. 14, or a top part of the tank 100 in a tank longitudinal center portion, as shown in FIG. 15.
Furthermore, the Patent Literature 2 discloses that at the time of molding the tank 100 that has a projection, such as a pipe, locally placed at one of two opposed longitudinal surfaces of the tank 100, two gate positions GP are respectively placed in a lateral surface of the tank 100 and the other one of the longitudinal surfaces of the tank 100, which does not have the projection, as shown in FIG. 18. According to the above prior art technique, a flow of the resin can be disturbed at the other one of the longitudinal surfaces, which does not have the projection. Therefore, shrinkage of the resin after the molding can be balanced between the side, which has the projection, and the other side, which does not have the projection. In this way, warping of the tank 100 can be limited.
However, in the case of FIG. 14, in which the gate position GP is placed in the lateral surface of the tank 100, and the case of FIG. 15, in which the gate position GP is placed in the top part in the center portion of the tank 100, the resin flows in the longitudinal direction (the left-right direction in FIG. 15) of the tank 100 at the top part of the tank 100 (the location, at which a center line O passes). The flow of the resin at this tank top part is a flow in a non-reinforcing direction with respect to a direction (an E-E direction, an F-F direction) of deformation of the tank 100, which is caused by an internal pressure load of the tank 100, as shown in FIGS. 16 and 17. That is, the glass fibers, which are added in the resin, are oriented in the longitudinal direction of the tank 100 (a direction perpendicular to a plane of the drawing). This is disadvantageous with respect to the strength and durability of the tank 100. FIG. 16 is a cross-sectional view taken along line XVI-XVI in FIG. 14, and FIG. 17 is a cross-sectional view taken along line XVII-XVII in FIG. 15.
Furthermore, in the case where the gate position GP is placed in the top part in the tank center portion, the gate position GP is located in a generating part of the maximum stress in the tank 100 caused by the internal pressure load. Therefore, the strength of the tank 100 may be disadvantageously deteriorated by a residual stress at the gate position GP.
In the prior art technique disclosed in the Patent Literature 2, the gage position GP is placed at the two locations, which are located in the lateral surface and the longitudinal surface, respectively, of the tank 100. Therefore, as shown in FIG. 18, the flow of the resin, which is filled from the gate position GP placed in the lateral surface of the tank 100, and the flow of the resin, which is filled from the other gate position GP placed in the longitudinal surface of the tank 100, are merged together from the different directions, respectively. Thus, a weld line is generated in a location, which is indicated by a dotted line in the drawing. This weld line is generated in the tank ceiling portion, which receives the maximum influence of the internal pressure load. Therefore, the strength and the durability of the tank 100 may be disadvantageously deteriorated.
Furthermore, in the structure of the Patent Literature 2, as shown in FIG. 19, the flow of the resin may be rapidly changed at the area adjacent to the projection 120. Thus, a substantial disorder may be generated in the orientation of the glass fibers. That is, in comparison to an H part in FIG. 19, at which the glass fibers are oriented uniformly in the longitudinal direction of the tank 100, the rapid change is generated in the orientation of the glass fibers at the area adjacent to the projection 120, as indicated in an I part in FIG. 19. Therefore, the strength of the tank 100 relative to the internal pressure load of the tank 100 tends to be deteriorated.